I am trying to find just how close a '68 standard gas cap should follow the contour of the tail panel.

I have a a reproduction tail panel. When I put my original filler tube and gas cap on, the fit was terrible. I attributed at least part of the problem to the fact that the flange on my original filler tube was out of whack. The angle of the flange to the tube wasn't consistant all the way around. I am sure the fact that the tail panel is a reproduction has something to do with it too.

I bought a new filler tube and gas cap from CHQ. The fit is better but the cap still sticks out a little at the top and about a 1/8 or 3/16 inch on the bottom. It stuck out a little on the sides but I was able to put a little pressure on the sides of the cap and bend it a little so that the side are fairly flush with the tail panel.

So my questions are: Were these gas caps completely flush with the tail panel all the way around when they left the factory or did they stick out some?

If they were flush, what can I do to get a better fit?

The attached photos are of the new cap. The second photo is from the top looking down. I could not get it to orient the right way.

Tailpanel is original. Not certain of cap, but I've subsequently replaced the cap with a repo at restoration and the fit is the same. My observation about 68 standard caps is they fit but not always perfectly flush and tight.

Yes I am...... The centering of the cap is not as bad as it looks in the picture. The angle I took it at and the flash caused a shadow making it look more off center...... I will adjust it to get it better though.

My tailpanel is original and the cap was an NOS one. Mine looks just like your as far as sticking out a little. I had a 68 ss and its cap fit that way too. My issue with the repop was that it didn't fit tightly on the gas tube. The NOS one is tight.